MATLAB: How to find x values given a FOR command

findMATLABmatrixx value

I need to find out what x values are created at certain intervals of t. t is in a matrix of 0:5:55; 
clear;
close;
clc;
a = 40*(pi/180);
v = 1200;
g = 32.2;
k=[0,2e-6,10e-6,20e-6];
k=0;
dt=.5;
t = 0:dt:55
vx = v*cos(a)
vy = v*sin(a)
x = zeros(length(t),4);
y = zeros(length(t),4);
x(1,1)=0;
y(1,1)=0;
vx(1,1)=vx;
vy(1,1)=vy;
for j=2:length (t)
    x(j,1) = x(j-1,1)+vx(j-1,1)*dt-.5*k*v(j-1,1).^2*cos(a)*dt.^2
    y(j,1) = y(j-1,1)+vy(j-1,1)*dt-5*k*v(j-1,1).^2*sin(a)*dt^2-0.5*g*dt.^2
    vx(j,1) = vx(j-1,1)-k*v(j-1,1).^2*cos(a)*dt
    vy(j,1) = vy(j-1,1)-k*v(j-1,1).^2*sin(a)*dt-g*dt
    a=atan(vy(j,1)./vx(j,1))
    v(j,1)=vx(j,1).^2+vy(j,1).^2
end
find (x) = 0:5:55
Transferring what I say in my head "find the x values from the equation when t=0:5:55
to the code is what is irking me

Best Answer

Replace
find (x) = 0:5:55
by 
x(1:round(5/dt):end,:)
This should work since 5/dt is a whole number. round takes care of a possible floating point error. When 5/dt isn't a whole number you can use the function interp1()
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